Telephone-exchange.



155 C and 2 the condenser is UNITED STATES; PATENT OFFICE.

SAMUEL A. .IIORS'IROllII, v OF CHICAGO, ILLINOIS, ASSIGNOR TO CASPER L. REDFIELD. OF

CHICAGQ ILLINOIS.

'rELnrnoNE-ExcmNGE,

Specification of Letters Patent.

Patented Nov. 12,1907.

Application filed July 13,1905. sernin zs9,44o.

certain new and useful Improvements in Telephone- I Exchanges, of which the following is a specification I My invention relates to telephone exchanges and for its object provision of means by which magnets .used for operating switching mechanisms are relieved 1 9 of their residual magnetism so that their armatures will I not stick to them when the circuit for operating them is broken.

In the accompanying drawing, I have illustrated a party line exchange in which the upper. part shows so much of the central office apparatus as is necessary to an a explanation, and the lower part shows the operating magnets of two local stations. In telephone exchanges having automatic operations, these operations are performed by magnets through which electrical impulses .20 are sent by an operator. In the kind of exchange chosen for illustration, the operator. is located at a central oflice andeach local station is provided with a switching mechanism operated by a magnet. When' the operator sends an impulse in one direction overthe 26" line, it causes the switching mechanisms to befadvanced by their magnets pd when she se'nd's one irf the opposite direction it causes the switching mechanisms to be released so that they may-return to their normal positions. In operating exchanges of this I SO kind an occasional trouble arises from an armature sticking to its magnet, thus causing theswitching mechanism where this occurs to fail to makeits proper movemerit I overcome this trouble by causing each oper- I impulse to be automatically followed by an im- I n'the releasing direction of such short duration flia' t is without effect on the magnets-other than to relieve. them of their residual magnetism. I accomthis result by providing at the central ofiice an extremely sensitive magnet, preferably high wound, 40 a cdndenser of large capacity, and an extra battery. These parts are connected to the othei central office devices in the manner shown. v

To operate the' exchange the operator turns the crank oi the calling device C, makinga series of connections to the point 2. Each time such connection is the current used to operate the magnets BfB, etc,

so as to advance their switching mechanisms. A

branch of this current flows from 3 by wa'y of 11 through I magnet A to the condenser 12, which becomes charged in consequence thereof. This current through A is in a direction which will hold the armature A its stop, but when the connection is broken betweenl discharged in theopposita direction through A. Owing to the'large capacity of the condenser 12, and the sensitive nature of the -magnet A, this discharge is sufficient to move the armature A so that the insulated springs thereon will niake a'brief connection with the adjacent contact points,

This is a current in the opposite directionthrough the.

magnets B, B etc., which destroys their residual magnetism due to the operating current and effectually prevents their armatures from sticking. v The length of time during which'this circuit is held, however, is sobrief that it is broken before the armatures of the magnets B, B etc. have moved anyappreciable distance,

and consequently it does'not cause release.

The operation for release is performed by pressing key 9 when a current flows: X18192(65- B-i-3152122910X. This current is the same in direction as that from battery Y but differs from it by being held long enough-to cause an operation of the magnets at the local stations. This is a natural result-of hand operation, it being difficult to close and open this connection quickly enough to prevent mechanical operations of the local station magnets.

What I claim is:-

1. The combination with a magnet provided with con nections by which electrical impulses may be sent through said magnet; of automatically operating means bywhich each such impulse through said magnet is followed by a second impulse sent inthe opposite direction through the magnet, the duration of said second impulse being suflicient to destroy the residual magnetism in said magnet but finsufficient to cause its operation in the opposite direction.

2. The combination with a polarized magnet adapted to be operated'in opposite directions by currents flowingin opposite directions through it, and a battery and connec tionsfor sending impulses in one direction through said magnet, of automatically operating means by which each such impulse is followed by a battery impulse in the oppo-,

site direction but of a duration insuilicient to cause a magnet movement in the opposite di ction. 1

3. The combination with a polar and means by 'which impulses in a given direction are .sent from said battery through said magnet, of a second magnet, and means by which upon completing an impulse through the first magnet said second magnet will cause a brief impulse of the kind described to flow in the opposite direction through'the first mentioned magnet.

4. The combination with a polarized magnet, a battery,

and connections by which impulses in a given direction are sent from said battery through said magnet, of a second magnet and a condenser bridged across said connections, means by which the discharge of said condenser' will cause said second magnet to close an electrical connection of very short duration, and means by which such clos ure will send a brief impulsein the opposite direction through the first mentioned magnet.

Signed at Chicago, Ill., this 7th day of July 1905.

' SAMUEL A. NORSTROM.

Witnesses A. L. Bucnsnni,

ed magnet, a battery, 7 

